[PATCH 5.10 353/406] af_unix: Fix data-races around sk->sk_shutdown.

Greg Kroah-Hartman
2023-09-17T19:40:44Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit afe8764f76346ba838d4f162883e23d2fcfaa90e ]

sk->sk_shutdown is changed under unix_state_lock(sk), but
unix_dgram_sendmsg() calls two functions to read sk_shutdown locklessly.

sock_alloc_send_pskb
`- sock_wait_for_wmem

Let's use READ_ONCE() there.

Note that the writer side was marked by commit e1d09c2c2f57 ("af_unix:
Fix data races around sk->sk_shutdown.").

BUG: KCSAN: data-race in sock_alloc_send_pskb / unix_release_sock

write (marked) to 0xffff8880069af12c of 1 bytes by task 1 on cpu 1:
unix_release_sock+0x75c/0x910 net/unix/af_unix.c:631
unix_release+0x59/0x80 net/unix/af_unix.c:1053
__sock_release+0x7d/0x170 net/socket.c:654
sock_close+0x19/0x30 net/socket.c:1386
__fput+0x2a3/0x680 fs/file_table.c:384
____fput+0x15/0x20 fs/file_table.c:412
task_work_run+0x116/0x1a0 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x174/0x180 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:297
do_syscall_64+0x4b/0x90 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x6e/0xd8

read to 0xffff8880069af12c of 1 bytes by task 28650 on cpu 0:
sock_alloc_send_pskb+0xd2/0x620 net/core/sock.c:2767
unix_dgram_sendmsg+0x2f8/0x14f0 net/unix/af_unix.c:1944
unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
sock_sendmsg_nosec net/socket.c:725 [inline]
sock_sendmsg+0x148/0x160 net/socket.c:748
____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
___sys_sendmsg+0xc6/0x140 net/socket.c:2548
__sys_sendmsg+0x94/0x140 net/socket.c:2577
__do_sys_sendmsg net/socket.c:2586 [inline]
__se_sys_sendmsg net/socket.c:2584 [inline]
__x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x6e/0xd8

value changed: 0x00 -> 0x03

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 28650 Comm: systemd-coredum Not tainted 6.4.0-11989-g6843306689af #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/sock.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index e2d45631c15d7..a971385a95d92 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2315,7 +2315,7 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
if (refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf))
break;
- if (sk->sk_shutdown & SEND_SHUTDOWN)
+ if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
break;
if (sk->sk_err)
break;
@@ -2345,7 +2345,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
goto failure;

err = -EPIPE;
- if (sk->sk_shutdown & SEND_SHUTDOWN)
+ if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
goto failure;

if (sk_wmem_alloc_get(sk) < READ_ONCE(sk->sk_sndbuf))
--
2.40.1